Contact arrangement for a compressed-gas circuit breaker

ABSTRACT

A contact arrangement is disclosed for a compressed-gas circuit breaker wherein the compressed gas is blown through the arc. The contact arrangement includes two contact pieces arranged on a common axis and having respective end faces mutually adjacent to conjointly define a gas therebetween. A switching member is movable between the open and closed positions to electrically join the contact pieces in the closed position and to electrically separate the contact pieces in the open position whereby an arc is drawn when the gap is opened. Each of the contact pieces has a hollow interior for accommodating the discharge of the gas blown through the arc and has an inner inlet surface defining an opening to the hollow interior. The inlet surface extends from the end face into the hollow interior. Each one of the contact pieces has a plurality of even grooves formed in the end face and the inlet surface thereof. Each of these grooves is skew at every increment thereof with respect to the common axis and extends tangentially into the opening at the inlet surface.

United States Patent [191 Heiner CONTACT ARRANGEMENT FOR A COMPRESSED-GAS CIRCUIT BREAKER [75] Inventor: Marin Heiner, Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany 22 Filed: Mar. 15,1973 21 Appl. No.: 341,472

[30] Foreign Application Priority Data Mar. 29, 1972 Germany 2215929 [52] US. Cl 200/148 R [51] Int. Cl. HOlh 33/60 [58} Field of Search 200/147 R, 144 B, 148 R [56] References Cited UNITED STATES PATENTS 3,327,081 6/1967 Pflanz 200/144 B 3,417,216 12/1968 Smith, Jr. 200/144 B FOREIGN PATENTS OR APPLICATIONS 1,965,800 6/1971 Germany 200/148 R 1,217,926 1/1971 Unitedlsingdom 200/148 R [451 Mar. 25, 1975 Primary Examiner-Robert S. Macon [57] ABSTRACT A contact arrangement is disclosed for a compressedgas circuit breaker wherein the compressed gas is blown through the arc. The contact arrangement includes two contact pieces arranged on a common axis and having respective end faces mutually adjacent to conjointly define a gas therebetween. A switching member is movable between the open and closed positions to electrically join the contact pieces in the closed position and to electrically separate the contact pieces in the open position whereby an arc is drawn when the gap is opened. Each of the contact pieces has a hollow interior for accommodating the discharge of the gas blown through the arc and has an inner inlet surface defining an opening to the hollow interior. The inlet surface extends from the end face into the hollow interior. Each one of the contact pieces has a plurality of even grooves formed in the end face and the inlet surface thereof. Each ofthese grooves is skew at every increment thereof with respect to the common axis and extends tangentially into the opening of the inlet surface.

4 Claims, 7 Drawing Figures CONTACT ARRANGEMENT FOR A COMPRESSED-GAS CIRCUIT BREAKER BACKGROUND OF THE INVENTION It is known to utilize the effect of magnetic fields to assist in the quenching of the arc in load and power circuit breakers. From Deutsche Offenlegungsschrift 1,088,580, a power circuit breaker is known wherein the are which is drawn between burn-off rings, rotates under the influence of magnetic forces within a cooling medium such as sulfur hexafluoride or the like. The magnetic field is generated here by two coils through which the arc current flows in opposite directions. In the known circuit breaker, a cooling medium can be pushed through the winding gaps of one or both coils in such a manner that it flows radially outward in the region between the coils. In this manner a stream of quenching gas acts on the arc transversely to the mag netic force of the magnetic field.

German Pat. No. 1,212,617 describes a contact arrangement for compressed-gas circuit breakers wherein the location where the power is interrupted consists of two jet tubes which are arranged at a fixed distance from each other and are provided with slots. By essentially radial slots in the nozzle-shaped contacts, a magnetic force which drives the are further into the interior of the hollow contacts is exerted on the arc in addition to the gas stream which is initiated during the opening motion. The disadvantage of the known configuration is that an effective magnetic blasting takes place only when the bases of the are are already situated on the end face of the contacts, so that a current loop generating the magnetic blasting field results. This means, however, that at the beginning of the opening motion, when the forces acting on the arc in the sense of a motion inward should be particularly great, the influence of the magnetic blasting is still small.

The are is furthermore driven radially inward in the known contact arrangement which means that the gas stream employed is utilized during the blasting of the are only to a small extent.

SUMMARY OF THE INVENTION Accordingly, it is an object of the invention to improve the effectiveness of the gas in extinguishing the arc in compressed-gas circuit breakers. Subsidiary to this object, it is an object of the invention to provide a contact arrangement wherein the arc is subjected to a force component transverse to the stream of gas blown at the are as well as a radial force component.

The contact arrangement according to the invention is utilized in a compressed-gas circuit breaker whereat the breaker is switched between open and closed positions. The contact arrangement includes as a feature two contact pieces arranged on a common axis and having respective end faces mutually adjacent to conjointly define a gap therebetween. A switching member is movable between the open and closed positions to electrically join the contact pieces in the closed position and to electrically separate the contact pieces in the open position whereby an arc is drawn when the gap is opened. Each of the contact pieces has a hollow interior for accommodating the discharge of the gas blown through the arc and having an inner inlet surface defining an opening to the hollow interior. The inlet surface extends from the end face into the hollow interior. To improve the quenching action of the arc drawn during the interruption process and according to a feature of the invention, each one of the contact pieces has a plurality of even grooves formed in the end face and the inlet surface thereof. Each of these grooves is skew at every increment thereof with respect to the common axis and extends tangentially into the opening at the inlet surface.

The invention makes it possible to provide the contacts with a shape which produces a magnetic field in the direction of the gas flow in such a manner that a force component which extends transversely to the gas stream as well as a radial component is exerted on the arc in addition to the gas stream. In this manner the quantity ofquenching gas which is brought into the gap during the interruption process is utilized with greater effectiveness. The shape of the grooves can be obtained in a particularly advantageous manner by cutting with a saw whereby complicated contours can be avoided.

The particular advantage the slots are filled with an arc-resistant insulating material in order that the gas flow the region of the end faces of the contact pieces is not distrubed. To improve the discharge of the hot switching gases, the insulating material filling the grooves can form a nozzle body arranged in the hollow space of the contact pieces.

According to another embodiment of the invention, the nozzle body can be lined on the side which directs the switching gases with an arc-resistant, electrically conductive material, preferably graphite.

Although the invention is illustrated and described herein as a contact arrangement for a compressed-gas circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the contact arrangement according to the invention are illustrated in the following FIGS. described below. Similar or like portions are designated by the same reference numeral in each FIG. in which they appear.

FIG. 1 illustrates, partially in section, the contact arrangement according to the invention. The contact arrangement constitutes part of a compressed gas circuit breaker of which part of the switching chamber is shown. The closed position of the circuit breaker is shown to the right of the center line and the open position to the left thereof.

FIG. 2 shows the end face region, in section, of one of the hollow switching contact pieces of the contact arrangement of FIG. 1.

FIG. 3 is an elevation view of the hollow contact piece of FIG. 2.

FIG. 4 is a plan view of the end face of the contact piece of FIG. 2.

FIG. 5 illustrates a contact piece according to an alternate embodiment of the invention.

FIG. 6 is a perspective view of the contact piece according to still another embodiment.

FIG. 7 is also a perspective view of the contact piece of FIG. 6 with a portion thereof cut away to afford a sectional view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In FIG. I, the contact system of a compressed-gas circuit breaker is shown. The circuit-breaker has a switching chamber 1 which can be made of porcelain for example and which contains a gaseous quenching and insulating medium in its interior 2, particularly, sulfur hexafluoride. In the interior space 2, two mutually adjacent contacts 3, 4 are arranged on a common axis and have respective end faces that conjointly define a gap 6. In the closed position of the breaker shown on the right of the center line, the two contacts 3 and 4 are electrically connected with each other by means of a switching member 7 which bridges the contacts, while to the left of the center line, the breaker is in the open position wherein the switching member 7 opens the gap 6. The contacts 3,4 have a U-shaped cross-section 8 and are hollow for the discharge of switching gases.

Referring to FIG. 2, in the region of their respective end faces 5, the contacts 3, 4 are provided with cuts 9 which are formed by even grooves which extend diagonally to the axis 10 of the contacts and run tangentially into the inner opening 11 of these contacts 3, 4. FIG. 3 shows that the grooves 9 are arranged inclined at an angle of about 45 to the axis 10 of the contacts.

FIG. 4 shows that the even grooves 9 which extend inclined at an angle to the axis of the contacts run tangentially into the inner opening 11. Already at the oc currance of an arc at any location of the end face of the contact, or even in the region of the outer surface 12 of the contact, this embodiment of theinvention develops a magnetic force which acts upon the arc to cause the arc to rotate about the axis of the contacts. The gas stream which starts simultaneously and is directed toward the interior of the contacts 3, 4 is utilized with greater effectiveness because the arc moves transversely to the gas stream. In the embodiment shown, the slots 9 are filled with an arc-resistant insulating material 14 such as a cycloaliphatic epoxy resin, which forms a nozzle body 15 arranged in the hollow spaced of the contacts 3, 4.

In the embodiment shown in FIG. 5, the nozzle body 15 carries a lining 16 of an arc-resistant, electrically conductive material such as graphite or the like. In this manner, the arc can be driven into the interior of the contacts 3, 4 and of the nozzles until it is extinguished so that the foot points of the arc cannot impede the discharge of the switching gases.

FIGS. 6 and 7 show a contact (3, 4) provided with the even cuts 9 according to a feature of the invention which run inclined at an angle to the axis 10 of the contacts and which open tangentially into the inner opening 11 of the contact (3, 4).

What is claimed is:

1. In a compressed-gas circuit breaker wherein the gas is blown through the are developed when the breaker is switched, a contact arrangement whereat the circuit breaker is switched between open and closed positions, the contact arrangement comprising two contact pieces arranged on a common axis and having respective end faces mutually adjacent to conjointly define a gap therebetween, each of said contact pieces having a U-shaped section, and a switching member movable between the open and closed positions to electrically join said contact pieces in the closed position and to electrically separate said contact pieces in the open position whereby an arc is drawn when said gap is opened, each of said contact pieces having a hollow interior for accommodating the discharge of the gas blown through the arc and having an inlet surface defining an opening to said hollow interior, said inlet surface extending from said end face into said hollow interior, each one of said contact pieces having a plurality of even grooves formed in the end face and the inlet surface thereof, each of said grooves being skew at every increment thereof with respect to said common axis and extending tangentially into said opening at said inlet surface, and arc-resistant, insulating material filling said grooves.

2. The contact arrangement of claim I, said insulating material being configured as a nozzle body mounted in said hollow interior.

3. The contact arrangement of claim 2, said nozzle body having a surface portion at the end face of the corresponding contact piece and having an inner wall, said surface portion and said inner wall conjointly defining a surface for guiding away the gas blown through the arc, and a lining of arc-resistant, electrically conductive material disposed on said surface portion and said inner wall of said nozzle body.

4. The contact arrangement of claim 3, said are resistant, electrically conductive material being graph- 

1. In a compressed-gas circuit breaker wherein the gas is blown through the arc developed when the breaker is switched, a contact arrangement whereat the circuit breaker is switched between open and closed positions, the contact arrangement comprising two contact pieces arranged on a common axis and having respective end faces mutually adjacent to conjointly define a gap therebetween, each of said contact pieces having a U-shaped section, and a switching member movable between the open and closed positions to electrically join said contact pieces in the closed position and to electrically separate said contact pieces in the open position whereby an arc is drawn when said gap is opened, each of said contact pieces having a hollow interior for accommodating the discharge of the gas blown through the arc and having an inlet surface defining an opening to said hollow interior, said inlet surface extending from said end face into said hollow interior, each one of said contact pieces having a plurality of even grooves formed in the end face and the inlet surface therEof, each of said grooves being skew at every increment thereof with respect to said common axis and extending tangentially into said opening at said inlet surface, and arcresistant, insulating material filling said grooves.
 2. The contact arrangement of claim 1, said insulating material being configured as a nozzle body mounted in said hollow interior.
 3. The contact arrangement of claim 2, said nozzle body having a surface portion at the end face of the corresponding contact piece and having an inner wall, said surface portion and said inner wall conjointly defining a surface for guiding away the gas blown through the arc, and a lining of arc-resistant, electrically conductive material disposed on said surface portion and said inner wall of said nozzle body.
 4. The contact arrangement of claim 3, said arc-resistant, electrically conductive material being graphite. 